Transport

• In order to live, all cells must take in

nutrients and eliminate wastes

• Nutrients and waste materials must cross

the cell membrane between the solution

outside the cell and the solution inside the

cell.

Concentration

• Amount of substance within a solution.

• Concentration gradient: The difference in

concentration of a substance from one

location to another. Movement along the

gradient occurs from high to low.

•Several processes are involved

in moving materials across the

cell membrane and can be

classified as either passive or

active transport

• Passive transport: the

movement of a

substance across a cell

membrane without the

input of the cell’s

energy – with the

concentration gradient

(high to low).

Examples include

diffusion, facilitated

diffusion and osmosis.

• Active transport: uses

cellular energy to

move substances

across a cell

membrane –

opposite of

concentration

gradient (low to

high)

Solutions

Solution: mixture of substances that is the same

throughout—it is homogenous. Example: Koolaid

Solvent: Water. (liquid substance that dissolves another

substance-water is the solvent for many solutions).

Solute: Often Solid particles that have a charge are

dissolved by water or other solvent liquid. Example:

sugar is a charged solid before mixing with water

Passive Transport: Diffusion

Cell Homeostasis

• Passive transport: Diffusion: the

random movement of solute or gas

from an area of higher concentration

(more molecules) to an area of low

concentration (fewer molecules)

Cell Homeostasis

• Simple diffusion enables oxygen and

carbon dioxide to cross the cell membrane

• Diffusion occurs down a concentration

gradient and does not require energy

from cell!

Think – Pair - Share

• What is going to make this

process happen faster?

• The rate of diffusion depends

on:

– Temperature

– Size of the molecule

Homeostasis: Passive Transport

•When the molecules are

evenly dispersed on both sides

of membrane. The net

movement is equal.

• This is called

equilibrium

Word play

•How are you going to

remember what equilibrium

means?

Nothing to write

•Some molecules diffuse

across the cell membrane

with the help of carrier

proteins in the membrane

• Facilitated diffusion: the

passive process of transporting

molecules by carrier proteins

during diffusion; requires NO

energy output-passive

transport.

• Always moves down a

concentration gradient from

an area of high concentration

to an area of low

concentration.

• ex: the movement of glucose from the blood

into body cells

Why?

Why do we need to get glucose

into our cells?

http://highered.mcgraw-

hill.com/sites/0072495855/student_view0/chapter2/animation__h

ow_facilitated_diffusion_works.html

Homeostasis

Facilitated diffusion Review:

1.Facilitated diffusion requires

A) enzymes. B) carrier transport proteins. C) lipid carriers. D) carbohydrate carriers. E) lipid or carbohydrate carriers.

2. Facilitated diffusion occurs

A) into the cell only. B) out of the cell only. C) in either direction depending on the temperature. D) in either direction depending on the concentration gradient of the molecules. E) in either direction depending on the size of the molecule.

3. Facilitated diffusion is used to transport

A) sugars and amino acids. B) H2O and O2. C) CO2 and O2. D) CO2 and H2O. E) sugars and H2O.

4. Unlike simple diffusion, facilitated diffusion requires energy expenditure by the cell. A) True B) False

5. Facilitated diffusion requires a specific transporter for a specific molecule. A) True B) False

Passive Transport:

Osmosis: the

diffusion

of water

across a

semi-

permeable

membrane

Osmosis

• Form of passive transport

• Occurs when the concentrations of

solutes in the membrane are

different

• Water moves from solutions with

high water concentration to

solutions with low water

concentration—water moves toward

solute/solid

Solutions

• Hypotonic: A solution that has a lower concentration

of solutes.

• Isotonic: Equal concentration of solutes on each side.

• Hypertonic: A solution that has a higher concentration

of solutes.

** These are comparison terms**

Cell Expands

Cell contents

are equal

Cell shrinks

Cell Homeostasis

Watch this: Osmosis/diffusion of substances through membrane (don’t

forget the QUIZ after!)

And

http://www.phschool.com/science/biology_place/labbench/lab1/ex1.h

tml

Osmosis and Turgor pressure

• Osmosis causes water from the environment to

move into the vacuole and pushes the

cytoplasm and cell membrane against the plant

cell wall. If the plant has enough water

available, the plant cells will stay rigid. If the

plant is lacking water, or the surrounding water

is hypertonic, water will leave the plant and it

will wilt.

Cell Expands equal Cell shrinks

Turgor pressure in a plant cell is analogous to

air pressure in a car tire;

Cell Homeostasis

Cells in hypotonic, isotonic, and hypertonic

solutions:

http://www.youtube.com/watch?v=IRQLRO3

dIp8

Cell Homeostasis

Example: Saltwater or

corn syrup Example: Distilled

water

Cell has more

solute than

solution

Gummy Bear Osmosis % change

• Step 1: Calculate Change (subtract original value from

the new value) (EXAMPLE: You had 5, but now you

have 7=2)

• Step 2: Divide that change by the original value (you

will get a decimal number) (EXAMPLE: 2/5= 0.4)

• Step 3: Convert to a percentage (by multiplying by 100

and adding a "%" sign) (EXAMPLE: 0.4 x100=40%)

• Note: if the new value is greater then the old value, it

is a percentage increase, otherwise it is a decrease.

Solutions

• For each of the following determine the solute and

solvent percentages for the solution outside the cell

(environment) and for the inside of the cell. Then...

• A) Tell whether the solution outside the cell is

hypotonic, hypertonic or isotonic.

• B) Give the direction of the net movement of water (

into the cell, out of the cell, or into & out of the cell at

equal rates)

• C) Tell what will happen to the cell (shrink, swell or

stay the same)

A. Hypotonic (80% water solvent)

B. Water will move inside the cell toward

solute

C. Cell will swell

Scenario-You stay in the pool or Lake

Unpleasant too long:

A. Hypertonic (90% solute-”salt” in this

instance)

B. Water will move outside the cell toward

solute

C. Cell will shrink

Scenario-You are stranded in ocean and

drink too much seawater

Solutions • What type of solution would have a 50%

each of solute (iodine) and solvent

(water)?

• What is the net movement of water in this

type of solution?

• What will happen to the cell?

If passive transport is going down a

slide, then what is active transport?

ACTIVE TRANSPORT: Movement of a substance

against a concentration gradient from areas of lower

concentration to areas of higher concentration

http://www.dnatube.com/video/1589/Cellular-

transprot-of-sodium-and-potassium-active-transport

Active Transport • Always requires energy

• Often involves carrier proteins

• The energy source for active transport is

ATP

• Active transport is important in

maintaining proper ion concentrations

inside the cell

• Helps with muscle contractions and

transmission of nerve impulses

• In plants, it enables roots to absorb

nutrients from the soil.

Active Transport examples:

• Endocytosis: Large molecules moved

into the cell via vesicle. There are two

types:

• http://www.susanahalpine.com/anim/

Life/endo.htm

1. Phagocytosis: The process by which

solid material is engulfed by a cell. – this

is how our white blood cells get rid of

foreign bodies in our blood.

http://www.cellsalive.com/mac.htm

Active Transport

2. Pinocytosis: Movement by vesicle in which

liquids are brought in or moved out of the cell.

This is used because they are unable to move

through the lipid bilayer.

Active Transport

• Exocytosis: Large particles moved out of

the cell via vesicle (the last stage of

endocytosis).

Cell Homeostasis

Summary of the passive and active methods of cell molecule transport:

• http://www.pbslearningmedia.org/resource/tdc02.sci.life.cell.membraneweb/c

ell-membrane-just-passing-through/

The proton pump is an indirect active transport used

by mitochondria and chloroplasts that gets its energy from

the potential energy of the concentration gradient of H+

protons.